The service environment and readiness of combat aircraft require quick installation and removal of engines and similar sub-assemblies from the aircraft. This operation must be performed at the depot level or in the field, and the personnel involved in the operation may be encumbered by hazardous or extreme environment protective equipment like special suits and gloves. For these reasons, quick disconnect attachment pins used in such instances should not require special tools and should be capable of being installed or removed by a single operator.
Structural attachment points commonly used in aircraft construction are of the lug and clevis type, or a variation thereof. The lug and clevis elements typically have an internal diameter lined with internal bushings. Internal bushings serve to line and protect the underlying structure or roller bearings commonly found in these locations. Installation of the engine or sub-assembly requires that these lugs and devises be brought into alignment so that a pin (clevis pin) can be inserted through the internal diameter and secured in place. Removal of the engine or sub assembly is the reverse of the mounting procedure. Jacks support the weight of the engine or sub-assembly while the lugs and devises are aligned to facilitate insertion or removal of the pin.
Clevis pins previously used in these applications are typically threaded fasteners like shear bolts and nuts, tapered solid pins, or expandable diameter fasteners. Threaded fasteners, by the nature of the threads, do not meet need the need for quick disconnection. Expandable diameter fasteners, even though they are quickly installed, are found to be difficult and time consuming to remove.
As such, whether heretofore recognized or not, there is a need for improved quick disconnect pins, particularly pins suitable for use with lug and clevis type joints of combat aircraft.